Under the proposed collaborative Phase I STTR grant by NCI, the Department of Surgery and the Center for Computer-Integrated Surgical Systems and Technology (CISST Center) of Johns Hopkins University will team up with the Image Guidance Division of Computerized Medical Systems, Inc. (CMS-IGD), with the intent to jointly develop a system that integrates 3D intra-operative ultrasound, robotically assisted needle placement, for the purpose of thermal ablation to treat liver tumors. Besides significant prior work and relevant professional expertise in the subject, the research will build on a two-year collaboration between the CISST Center and CMS-IGD in ultrasound-guided minimally invasive procedures. The existing collaboration has been funded by a Phase II and two Phase I joint SBIR grants from the National Cancer Institute. Studies have demonstrated the efficacy of treatment of hepatic tumors with various forms of interstitial ablation. Despite all therapeutic advancement, however, precise placement of the ablator device and inducing a well-controlled necrotic lesion are unsolved problems. Intra operative ultrasound (IOUS) provides excellent differentiation of soft issue, but simultaneous manual handling of the IOUS probe and the tissue ablator is prone to significant errors in the hands of even the most experienced physicians. Tissue deformation and target motion make it extremely difficult to place the ablator precisely into the target. We propose to integrate three-dimensional intra operative ultrasound (3D-IOUS) with an active lightweight robotic arm to facilitate precise placement of a needle ablation probe into the liver and to monitor the progress of tissue ablation in real-time ultrasound. Contemporary surgical robots require complex engineering entourage that involves prohibitively high costs. We will focus on radio frequency thermal ablation as initial therapeutic method, with the understanding that this system can be adapted for use with a variety of thermal and non-thermal ablative methodologies. In contrast to those, a specific goal of this project is to demonstrate full functional capability with a simple, lightweight and inexpensive system.